Fair value measurements - Assets and Liabilities Not Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes receivable, net	$ 57,495	$ 53,983	[1]
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	112,433	213,759
Restricted cash	25,534	127,765
Deposits with clearing organization	52,754	37,885
Securities borrowed	127,817	99,752
Receivables from brokers	49,125	39,716
Securities failed to deliver	9,099	9,212
Clearing organizations and other	20,035	19,518
Other		1,693
Total Receivable from brokers, dealers and clearing organizations	206,076	169,891
Receivable from customers	1,202,764	1,221,450
Securities purchased under agreements to resell		935
Notes receivable, net	57,495	53,983
Investments	79,322	99,169
Bank call loans	0	69,500
Securities loaned	320,843	244,223
Payable to brokers	123	2,077
Securities failed to receive	62,646	6,457
Other	166,350	169,013
Total payables to brokers, dealers and clearing organizations	549,962	421,770
Payables to customers	456,475	456,958
Securities sold under agreements to repurchase	161,009	277,322
Senior secured notes	113,233	131,094
Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	112,433	213,759
Restricted cash	25,534	127,765
Deposits with clearing organization	52,754	37,885
Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities borrowed	127,817	99,752
Receivables from brokers	49,125	39,716
Securities failed to deliver	9,099	9,212
Clearing organizations and other	20,035	19,518
Other		1,693
Total Receivable from brokers, dealers and clearing organizations	206,076	169,891
Receivable from customers	1,202,764	1,221,450
Securities purchased under agreements to resell		935
Notes receivable, net	57,495	53,983
Investments	79,322	99,169
Bank call loans	0	69,500
Securities loaned	320,843	244,223
Payable to brokers	123	2,077
Securities failed to receive	62,646	6,457
Other	166,350	169,013
Total payables to brokers, dealers and clearing organizations	549,962	421,770
Payables to customers	456,475	456,958
Securities sold under agreements to repurchase	161,009	277,322
Senior secured notes	113,233	131,094
Nonrecurring | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	112,433	213,759
Restricted cash	25,534	127,765
Deposits with clearing organization	52,754	37,885
Securities borrowed	127,817	99,752
Receivables from brokers	49,125	39,716
Securities failed to deliver	9,099	9,212
Clearing organizations and other	20,035	19,518
Other		1,693
Total Receivable from brokers, dealers and clearing organizations	206,076	169,891
Receivable from customers	1,202,764	1,221,450
Securities purchased under agreements to resell		935
Notes receivable, net	57,495	53,983
Investments	79,322	99,169
Bank call loans	0	69,500
Securities loaned	320,843	244,223
Payable to brokers	123	2,077
Securities failed to receive	62,646	6,457
Other	166,350	169,013
Total payables to brokers, dealers and clearing organizations	549,962	421,770
Payables to customers	456,475	456,958
Securities sold under agreements to repurchase	161,009	277,322
Senior secured notes	$ 114,050	$ 125,000

[1] (1) Certain prior period reported amounts were reclassified to conform to the current period presentation, See Note 2.